This project seeks to define and characterize specific antibodies and glycoconjugates which protect infants from infection and disease due to rotavirus. We previously have shown that the presence of serum and intestinal anti-rotavirus antibodies are associated with protection against rotavirus disease, but these observations are preliminary and need further characterization. We hypothesize that human milk contains antibodies and glycoconjugates that protect suckling infants from disease due to rotavirus. This hypothesis will be addressed by the following specific aims: Specific Aim 1: To correlate serum rotavirus VP7 specific neutralizing antibody with outcome of rotavirus infection in our cohort of breastfed and non- breastfed Mexican infants and toddlers monitored prospectively for the past four years. Specific Aim 2: To determine whether pre-existing milk and/or intestinal homotypic or heterotypic anti-rotavirus antibody conferred protection against infection or disease in human infants. Specific Aim 3: To determine the association between concentration of mucin (glycoprotein) in maternal milk and protection against rotavirus infection and diarrhea in suckling infants. Specific Aim 4: To continue to evaluate the immune response of postpartum women to rotavirus vaccine and correlate the response with protection against rotavirus infection and disease in suckling infants born to these women. Information from these studies will help us to develop intervention and prevention strategies to decrease the morbidity and mortality associated with rotavirus disease.